Just go to every branch of any bank until you get an account opened. The letter from British Embassy is not always needed. If you have a Thai wife take her with you, take as much paperwork with you as possible, marriage certificate etc.
Kool BreezI did my second 90 day report online on the exact day the piece of paper said and it was refused for being late! So I had to go in person again. Since then I have done my third report online and it was successful, I did it 14 days early.